Complex processes govern lung inflammation and defenses against infection. ARDS appears to represent a disordered lung inflammatory response. The development of new therapies for this disorder are likely only to follow improved understanding of the fundamental processes controlling lung inflammation. This project seeks to explore the role in lung inflammation of two cell types poised at the anatomical interface between the lung and external environment: airway and alveolar epithelial cells and lung macrophages, and in these cells of NF-kappa B. NF-kappaB proteins play a key role in the transcriptional regulation of multiple genes, the products of which regulate inflammation, immunity and apoptosis. This project will address the following specific aims: (1) To determine the role of NF-kappa B dependent gene expression by the distal airway and alveolar epithelium in the lung response to LPS or bacterial infection, through the generation of transgenic mice in which dominant negative IkBa or RelB is expressed selectively in these cells under the control of the surfactant apoprotein C promoter. (2) To determine whether varying the time and magnitude of NF- kappaB modulation in distal airway and alveolar epithelium alters the nature of the lung response to LPS or bacterial infection. This will be done by generating transgenic mice in which expression of the ecdysone receptor is directed to these cell types under the control of the surfactant apoprotein C promoter and dominant negative IkB is expressed under the control of the surfactant apoprotein C promoter and dominant negative IkB is expressed under the control of an ecdysone responsive promoter. (3) To compare the role of NF-kappaB dependent gene transcription by lung macrophages versus lung epithelial cells in the pulmonary response to LPS or bacterial infection. This aim will be addressed by comparing the response in transgenic mice in which dominant negative IkBa is expressed selectively in macrophages under the control of the CD68 or lysosome gene regulatory elements, to the response of mice described in Aims 1 and 2. For comparison liposome-encapsulated clordronate mediated depletion of alveolar macrophages will be used, since this is an established method to assess the contribution of this cell population to lung inflammation and infection. The response to LPS and bacterial (K pneumoniae and P aeruginosa) challenges to the lung will be assessed in the different groups of mice through assessment of neutrophil recruitment, lung vascular leak, cytokine/chemokine and adhesion molecular expression, and alterations in lung surfactant aproprotein expression and apoptosis. Together these aims will evaluate, using novel reagents and approaches, the role of lung epithelium and lung macrophages in the regulation of lung inflammation, defense and cellular homeostasis.